Safety circulation medium for well casings



Nov. 7, 1939. R. c. BAKER 2.178.845

SAFETY CIRCULATION MEDIUM FOR WELL CASINGS Filed 001;. 10, 1936 IN VEN TOR.

AJLTORNEY Patented Nov. 7, 1939 UNITED STATES PATENT OFFICE SAFETY CIRCULATION MEDIUM FOR WELL CASINGS Reuben C. Baker, Coalinga, Oalifi, assignor to Baker Oil Tools, Inc.,

Huntington Park, Califi,

3 Claims.

This invention relates to the operation of casing deep oil wells.

There are instances during the lowering of the casing into an oil well bore, or during the cementing of the same in an oil well bore, that circulation downwardly through the casing is shut off. This may be caused by clogging of the casing or fittings on the casing along its length, or due to circumstances and conditions which prevent fluid from passing upwardly beyond a certain point along the casing between it and the wall of the bore. The many other reasons and circumstances which cause prevention of circu lation downwardly through the casing are well known to those skilled in the art and are too numerous to set forth here.

It is the principal object of my present invention to fit the well casing with means uninterfering with circulation downwardly through the casing in the usual manner under normal conditions, but which means is responsive to increased pressure in. the casing resulting from the shutting ofi of such normal circulation to provide a means of circulation above the point of shut-oil.

In practicing my invention, I fit the casing intermediate its ends with a medium which is responsive to increased pressure within the casing to permit circulation through the side wall of the casing. The pressure to which such medium is responsive is preferably definitely greater than the pressure required for normal circulation downwardly through the casing and upwardly between it and the walls of the hole.

One form which the invention may assume is exemplified in the following description and illustrated by way of example in the accompanying drawing, in which:

Fig. 1 is a diagrammatic view showing a casing positioned in a well bore and constructed in accordance with my present invention.

Fig. 2 is an enlarged view in section of the casing showing my improved circulating plug fitted thereto.

Fig. 3 is an enlarged view in external elevation of the device shown in Fig. 2.

Fig. 4 is an enlarged fragmentary view in vertical section through the three ports disclosed in Fig. 1, showing the different diameters of the shear pins connecting the, closure means to the casing.

Referring more particularly to the accompanying drawing, l0 indicates an oil well bore and II indicates the water string of blank casing therein. As previously pointed out the present invention is concerned with a safety medium for opening a circulation port in the casing intermediate its ends when circulation cannot 'be established through the lower .end of the casing. For this purpose the casing is formed with a radial aperture II a through its side wall which is internally 5 threaded to receive a bushing l2. The aperture I la may be formed in a fitting interposed between casing lengths or may be formed directly in the casing itself, if it is so desired, and when I use the term casing herein, I mean either the cas- 10 ing lengths pro-per or 'any fittings connected therewith.

The bushing I2 is bored coaxially as at l5 so as to form a circulation port communicating at its inner end with the interior of the casing and 15 at its outer end with the space exteriorly of the casing. Slidably fitting within the circulation port or bore I5 is a plug l6 which is hollow and cylindrical. The outer end of this plug I6 is closed as at IT and the inner end thereof is open 20 as illustrated. The inner end of the plug is surrounded by an exterior annular fiange iii of a diameter greater than the circulating port or bore IS. The length of the plug between the annular flange l8 and its closed outer end I! is greater 25 than the length of the port or bore I5.

The side wall of the plug I 6 is formed with a radial port I9 closely adjacent to its outer end, as most clearly illustrated in Fig. 2. A transversely arranged shear pin 20 normally secures 80 the plug IS in the bore or circulating port l5 with its outer end flush with the exterior of the casing. In this position the radial port l9 in the ping I 6 is covered by the wall of the bore I 5 so that it will be inefiective to permit circula- 35 tion through the plug and casing. The shearing strength of the pin 20 is so calculated that it will be sheared when the pressure on the plug from within the casing exceeds a predetermined value. I prefer that this pressure he definitely 40 greater than the pressure normally necessary to establish and maintain circulation through the casing in the usual and normal manner. The margin of difference between the pressure necessary to maintain normal circulation and that necessary to shear the pin 20 depends, of course, on the operators judgment and the depth of the well into which the casing is interposed.

When the pressure builds up in the casing to the predetermined point, the pin 20 will be sheared 50 and the plug IE will be moved radially outward with respect to the casing until the flange l8 engages the inner periphery of 'the casing, at which time the port ill will be uncovered and disposed beyond the exterior of the casing so that circulation can be established through the circulating port [5 from the'interior of the casing to the space surrounding the exterior thereof.

It is obvious that should the auxiliary circulating port l5 and its associate mechanism just described be fitted to the casing at a point above its lower end and circulation should, for any reason, be shut off below such auxiliary circulating port, that a'definite and predetermined rise of pressure inthe casing will be followed by shearing of the pin 20 and opening of the circulating port [5 so that circulation may be established at that point along the casing. v

It is obvious, of course, that when circulation is shut ofi at the lower end of the casing that the pressure in the casing will automaticaly rise until that pressure required to open the auxiliary circulating port I5 is reached.

In a long string of casing, as illustrated in Fig. 1, I may prefer to use more than one auxiliary circulating port l5 and I prefer that they be opened in response to progressively increasing pressures in the casing in an upward sequence. This is accomplished, of course, by merely progressively increasing the diameter of the shear pins 20a and 20b of the upper closures of the circulating ports as shown in Fig. 4. In this ar-- rangement circulation may be established at the lowest possible point above the point of shut-off so that. if circulation cannot be eflected through the lower end of the casing, the pressure will rise to the point sufilcient to open thefirst auxiliary circulating port, and if circulation cannot be broken. at that point, pressure in the casing will rise to open the next uppermost circulating port i511 and so on until circulation is established.

From the foregoing it is obvious that I have provided a very eflicient medium for enabling circulation to be broken through the side wall of a blank string of well casing above the point where circulation could not be established or maintained.

While I have shown the preferred form of my invention, it is to be understood that various changes may be made in its construction by those skilled in the art without departing from the spirit of the invention as defined in the appended claims.

Having thus described my invention, what I claim and 'desire to secure by Letters Patent is:

1. In combination with a string of blank well casing, said casing having a circulation port formed therein at an intermediate point therealong, a closure for said port, a shear pin normally maintaining said closure effective, said shear pin being capable of being sheared by a predetermined pressure in the casing to render said closure inefiective.

2. In combination with a string of blank well casing, said casing having a plurality of circulation ports formed therein at longitudinally spaced intermediate points therealong, a closure for each port, shear means for each closure normally maintaining the same effective, said shear means being sheared in an upward sequence in response mg the same, a shear pin connecting said plug. 

